The present invention relates to an exhaust gas purification device of an internal combustion engine that is used in a vehicle such as an automobile. Particularly, the present invention relates to an exhaust gas purification device of an internal combustion engine, which may purify nitrogen oxides (NOx) contained in an exhaust gas of the internal combustion engine using an exhaust gas purification solution.
An exhaust gas purification device of an internal combustion engine, e.g., a diesel engine or a gasoline engine, is taught by, for example, Japanese Laid-Open Patent Publication No. 9-511807. In this device, an aqueous solution of urea contained in a storage tank is injected into an exhaust gas of the internal combustion engine via a solution supply line, so that the exhaust gas is purified.
In the exhaust gas purification device thus constructed, the aqueous solution of urea must be prevented from freezing in the solution supply line in order to prevent damage of the solution supply line. For this purpose, this device is designed such that a pressure gas is pumped from a pressure gas container into the solution supply line using a pressure pump when the internal combustion engine is stopped, so that the aqueous solution of urea in the solution supply line may preferably be returned into the storage tank by the pressure gas. However, this structure requires the pressure gas container, the pressure pump or other such devices. This may lead to increased size of the exhaust gas purification device.
Thus, there is a need in the art for an improved exhaust gas purification device of an internal combustion engine.